Events During the Week of
March 10th through March 17th, 2013

Abstract: Please visit the following link for more details:http://cmb.physics.wisc.edu/journal/index.html
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Le Zhang (lzhang263@wisc.edu)

Abstract: In this talk, I will discuss methods to compute the efficiency of a microwave photon detector based on a current-biased Josephson junction (JJ), which is either connected to a (driven) microwave resonator or driven directly by a classical microwave source. Here I consider the evolution of the system in the presence of the environment and tunneling events of the JJ to the voltage state. I will then discuss how one can use the waiting time distribution to compute the average switching rate of the JJ and the efficiency of the photon detector. Finally, I will present a preliminary result on the condition for power matching between the detector, which I treat as a linear oscillator, and the microwave source.

Abstract: The direct and indirect consequences of climate change on forests of North America are only beginning to unfold. Tree health will be directly affected by changing temperature and precipitation patterns. However, just as important are the effects of a changing climate on many of the natural disturbance processes such as wildfire and insect outbreaks that have shaped forest ecosystems for millennia. As trees are relatively long-lived organisms, climate-driven changes to forest ecosystems may be subtle until a disturbance catalyzes change and sends the system along a new trajectory. This talk will include a look into what we can expect in western forests under new climatic and disturbance regimes.<br>

Abstract: A series of weekly presentations and discussions of current research topics in physics by the scientists involved in those studies designed to expose students to the topics and excitement of the research frontier.

Abstract: The lack of observation of superpartners at the Large Hadron Collider so far has led to a renewed interest in supersymmetric (SUSY) models with R-parity violation (RPV). With the additional assumption of holomorphic Minimal Flavor Violation (MFV), baryonic RPV dominates and the strongest bounds can be evaded. I demonstrate the sensitivity of same-sign lepton searches at the LHC to MFV/RPV SUSY in two different scenarios. In the first, production of neutral "mesinos" which oscillate yields an observable signature. In the second, production of Majorana gluinos generates same-sign leptons with large production cross-section. I reinterpret current results to place bounds on these scenarios and discuss methods to enhance the signature in future searches.

Abstract: Please join us for a conversation on "Careers for Physicists" with Scott Converse. Scott got his undergraduate degree in physics from UW-Eau Claire and had originally planned on either teaching high-school physics, or going on to do graduate work that would prepare him for a career in astrophysics. Quickly that plan changed and he ended up working in software development, IT management, project management, business management, and eventually teaching adult professionals. Scott received his MBA from UW-Madison is currently the director of project management and process improvement programs for the Wisconsin School of Business. He also oversees the Technical Leadership, a joint effort between the College of Engineering and Wisconsin School of Business that was created to help the technical professional successfully transition into a successful manager. His bio can be found at: http://bus.wisc.edu/faculty/scott-converse

Abstract: Over the last ten years, experimental advances with ultracold quantum gases in optical lattices have made possible the study of various interesting many-body phenomena that are difficult to observe in solid-state systems. Not only do these systems allow the investigation of interesting quantum phases, but they offer unique opportunities for the study of non-equilibrium dynamics, addressing fundamental questions such as the mechanisms behind thermalization in closed quantum systems or the behavior of a system after a quantum quench. I will discuss our recent work in coherent and dissipative many-body dynamics, focused around these ideas as well as the key challenge in experiments of producing many-body states with low temperature and entropy. In this context it is important to characterize and control the competing heating mechanisms in the experiment, which can arise from various sources, including incoherent scattering of the lattice light (spontaneous emissions), and typically have effects that depend strongly on the detailed characteristics of the many-body state. Spontaneous emissions tend to localize atoms on particular lattice sites, in that sense acting as a type of local quantum quench. Computing dynamics described by a many-body master equation, we investigate such quenches for bosons moving in 1D in the lattice system. We identify both regimes in which simple observables relax rapidly to a thermal distribution at higher temperature, and other regimes where the system settles on a short timescale to a non-thermal state. I will also discuss adiabatic state preparation techniques, and how they could be useful in preparing many-body states in a variety of systems, including crystalline states of Rydberg atoms.

Abstract: We study the semi-classical dynamics of four dimensional gauge theories with adjoint fermions compactified on a circle with periodic boundary conditions for the fermions. There are monopole-instantons (with fermion zero modes) and two types of monopole--anti-monopole molecules, called bions. The plasma of the type-one bions--- which carry net magnetic charge---induces a mass gap for gauge fluctuations. The type-two bion is both topologically and magnetically neutral, and its understanding requires a generalization of multi-instanton techniques in quantum mechanics to compactified field theory. We conjecture that it is the semi-classical realization of four-dimensional IR renormalons.

Abstract: The confinement of quarks inside protons and neutrons is thought to follow from the theory of the strong force, quantum chromodynamics (QCD). By now very convincing numerical evidence for this has been found by computer simulations of QCD, but an actual derivation of confinement using analytical techniques has resisted all attempts to date. This talk will review the concepts and problems involved in trying to explain confinement analytically, and will present some recent work that sheds light on when and how confinement arises when QCD and similar theories are given periodic boundary conditions in one spatial direction.